Re: [Qemu-devel] [edk2] (PAM stuff) reset doesn't work on OVMF + SeaBIOS CSM

[H. Peter Anvin]

On 02/14/2013 12:41 PM, Laszlo Ersek wrote:
> 
> ). cpu_reset() [target-i386/helper.c] sets CS:IP to f000:fff0, which is
> the exact address of... reset_vector() in SeaBIOS.
> 

This would be a bug, but it isn't quite true.

If you look at x86_cpu_reset() you will note that it sets the code
segment base to 0xffff0000, not 0xf0000 as one could expect from the
above.  This is also true of a physical x86.

As such, the *real* reset vector is at 0xfffffff0 as opposed to the
SeaBIOS vector at 0xffff0 -- this is a backwards compatibility vector
which typically just issues a real reset.

Now, if Qemu doesn't handle the distinction here correctly, that is a bug.

        -hpa